The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Additive manufacturing devices produce three-dimensional parts by sequentially adding materials in a pattern. Some classes of additive manufacturing devices produce polymer parts solidified from a photopolymer resin which has been exposed in a layer-wise fashion to electromagnetic radiation generated by a light source such as a projector. The light source projects a cross sectional image into a build area, solidifying a layer of photopolymer resin into a hardened layer, thereby adding another layer to the object being formed. Ideally, energy output from the light source would be precisely controlled and uniform across the build area for a single light source. Furthermore, consistency from light source to light source is desired when producing such additive manufacturing devices in quantity.
Consistent energy output is essential because the photopolymer resin only hardens into a solid form when exposed to sufficient flux of a specific wavelength of light. If an area to be hardened is not exposed to a sufficiently intense burst of light, it will not solidify in a desirable fashion. Additionally, if an area to be hardened is overexposed, the area will over harden, or “overcure,” which may hamper the building process by, for example, sticking to the build area surface or hardening more resin than required, thereby creating a deformed or failed build. Overcuring often occurs where a light source “hotspot” exists. A hotspot is an area of high relative light intensity.
In order to create consistent energy output from a light source, previous additive manufacturing devices have been calibrated using costly and specialized equipment. In one process, a light meter is set up above the build area of the additive manufacturing device. The light source displays a test pattern (e.g., full brightness across the build area) and the light meter measures the actual output at various points within the build area, creating a “map” of light output. Absolute maximum and absolute minimum are determined. Where the light source is a pixel-based projector, such as a digital micromirror device-based projector, light output may be measured at each pixel or for discrete groups of pixels. Brightnesses of controllable elements (e.g., pixels) of the light source are adjusted such that uniform light output is achieved. This is often accomplished by dimming all controllable elements of the light source to the measured absolute minimum. Although this method may provide a uniform light source, build times are increased due to reduced energy flux into the photopolymer resin. The full range of energy output is not used.
Over the life of an additive manufacturing device, it is often necessary to recalibrate the light source in order to ensure uniformity. In particular, the light source may comprise a bulb which must be replaced every 400-1,000 hours of operation. When the bulb is replaced, the additive manufacturing device must be recalibrated in order to ensure uniform and predictable light production. Current methods of light source calibration require additional equipment necessitating a costly on-site visit by a calibration technician, renting of the appropriate equipment, or purchase of such equipment.
Given the foregoing, what is needed are systems, methods, and computer program products which facilitate uniform light production by additive manufacturing light sources without utilizing additional equipment. Furthermore, calibration methods which are easily implemented by the user are needed.
Additionally, what is needed are systems, methods, and computer program products which dynamically use a broader range of energy outputs from an additive manufacturing device light source.